1. Field of the Invention
The present invention relates to a window treatments, and more particularly, to a motorized venetian blind system.
2. Description of the Related Art
Window treatments, such as, for example, roller shades, draperies, roman shades, and venetian blinds, are normally mounted in front of windows to provide for control of the amount of sunlight entering a space. A typical venetian blind system comprises a number of elongated slats extending along the width of the window and spaced apart vertically between a head rail and a bottom rail. The blind system typically comprises a lift cord that extends from the bottom rail through openings in the slats to the head rail and provides for lifting the bottom rail to raise and lower the slats. In a manual blind system, the end of the lift cord that is not attached to the bottom rail often hangs down from the head rail, such that a user may pull on the lift cord to raise and lower the slats. The blind system also typically comprises a tilt ladder that extends between the head rail and the bottom rail and operates to support and tilt the slats. Typical prior art manual blind systems include a rod that hangs from the head rail and may be rotated to adjust the tilt angle of the slats. The slats may be oriented substantially horizontal (i.e., perpendicular to the window) to allow sunlight to enter the space, and may be oriented substantially vertical (i.e., parallel to the window) to prevent sunlight from entering the space.
Some prior art venetian blind systems have included a motor to provide for lifting and tilting the slats. Such motorized venetian blind systems typically comprise a single motor coupled to a drive shaft that extends across the width of the head rail. The drive shaft may have at least two drums for winding up the lift cords when the shaft is rotated by the motor. The tilt ladders are typically coupled to the drive shaft through frictional force, such that when the slats have been fully tilted in one direction, the ends of the tilt ladder slip by the drive shaft as the drive shaft is rotated. To adjust the tilt of the slats, the drive shaft may be rotated in the reverse direction, such that the frictional force between the tilt ladder and the drive shaft causes the ends of the tilt ladder to rotate. Accordingly, the motor must be rotated in the reverse direction to adjust the tilt of the slats in typical prior art motorized venetian blind systems that comprise a single motor. This can be disadvantageous when, for example, the bottom rail is lowered to a fully-lowered position. In order to adjust the tilt of the slats in this condition, the bottom rail must be raised from the fully-lowered position, thus allowing sunlight to enter the space.
Thus, there exists a need for a motorized venetian blind system that has more accurate and flexible control of the position of the bottom rail and the tilt angle of the slats.